Making the Mirror for the World’s Largest Telescope

Workers completing the mold of the 8.4 metre mirror for the Giant Magellan Telescope mirror. Image credit: Lori Stiles/UA. Click to enlarge.
The University of Arizona’s Steward Observatory Mirror Lab is pre-firing its huge spinning furnace and inspecting tons of glass for casting a first 8.4-meter (27-foot) diameter mirror for the Giant Magellan Telescope (GMT). The casting is scheduled for Saturday, July 23.

With this milestone step, the GMT becomes the first extremely large ground-based telescope to start construction.

The completed GMT telescope primary mirror will consist of six 8.4-meter off-axis mirrors surrounding a seventh, on-axis central mirror. (An off-axis mirror focuses light at an angle away from its axis, unlike a symmetrical mirror that focuses light along its axis.) This arrangement will give the GMT four-and-one-half times the collecting area of any current optical telescope and the resolving power of a 25.6-meter (84-foot) diameter telescope, or 10 times the resolution of the Hubble Space Telescope.

‘Spin-casting’ single-piece telescope mirrors that are giant, stiff yet lightweight is an ingenious, awesome process that was conceived and developed by University of Arizona Regents’ Professor of astronomy J. Roger P. Angel. Casting giant monolithic mirrors is accomplished at only one place in the world — the Steward Observatory Mirror Laboratory.

The casting team, headed by Randy Lutz, installed about 50 cores a day for a total 1,681 cores during seven weeks in April – May. The team bolted each core at precisely measured angles to hearth tile and adjoining cores in this operation. The crew daubed all the glued junctures with blue “smurf” – a concoction the color of the blue smurf cartoon characters — to prevent glass from sticking to the mold.

At this point, the mold holds 17,000 pounds of hearth tiles, 16,000 pounds in fiber tub walls, and 15,000 pounds of cores and pins. The casting team has now cleaned and inspected the completed mold, lowered the furnace cover into place, and begun pre-firing on June 16.

Team members actively ‘pilot’ the furnace by computer as temperatures ramp up during the first 8 days of the heating process, then shut power off to complete the two-week pre-firing. Pre-firing centers core glue joints, burns out any impurities and stresses the mold. The casting team will inspect the mold for any needed repairs after pre-firing.

Some of the most visually stunning steps in casting are glass inspection and loading. The team began inspecting 90 shipping crates of glass on June 24. Glass loading is scheduled for the second week of July, said Steve Miller, Mirror Lab manager.

The 40,000 pounds of borosilicate glass that will make the 27-foot diameter (8.4 meter) GMT mirror comes from Ohara Glassworks in Japan. Ohara made the glass from sand that comes from the gulf coast of Florida.

The Mirror Lab will start heating the furnace July 18. It takes six days for the glass to reach peak temperature at 2,150 degrees Fahrenheit (1178 Celsius). At this temperature, the glass begins to flow like honey at room temperature. The thick liquid glass flows between the hexagonal cores in the mold to create a “honeycomb” structure. The final honeycomb mirror blank will weigh about a fifth as much as a solid glass mirror of its size.

The bearings on the rotating furnace will turn a 100-ton load during spincasting. The furnace can be supplied with up to 1.1 Megawatts of electricity during casting — enough to power an average 750 to 1,100 Tucson households, depending on the time of year.

The oven’s rotation rate determines the depth of the curve spun into the shape of the mirror, or the mirror’s focal length. The GMT mirror will spin 5 times a minute, slower than the two 8.4-meter mirrors the Lab made for the Large Binocular Telescope (LBT), because the off-axis GMT mirror is to be a shallower, longer focal-length mirror than the symmetric LBT primaries.

“This is a new epoch for astronomy,” Richard Meserve, president of the Carnegie Institution, said. “The fabrication of the off-axis mirror is a path-breaking event that will advance scientific discovery. Everyone in the eight-member GMT consortium is excited that we’re in production.”

The Giant Magellan Telescope consortium currently includes the Carnegie Observatories, Harvard University, Smithsonian Astrophysical Observatory, University of Arizona, University of Michigan, Massachusetts Institute of Technology, University of Texas at Austin, and Texas A & M University.

“The fact that we are already in production is directly related to the successful technology developed for the twin 6.5-meter (21-foot) Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile,” said Matt Johns, assistant director of the Carnegie Observatories and GMT project manager. “The Magellan telescopes have proved to be the best natural imaging telescopes on the ground.”

Mirror cooling is a carefully controlled process that will take 11 to 12 weeks. After the mirror is completely cooled, the lab will wash the ceramic cores out of the mirror’s glass honeycomb cells. Then the mirror will be ground and polished to an accuracy of plus-or-minus 15 to 20 nanometers (a nanometer is a billionth of a meter). The mirror will be coated with a layer of reflective aluminum only 100 nanometers thick at the observatory site.

The GMT is slated for completion in 2016 at a site in northern Chile. With its powerful resolution and enormous collecting area, it will be able to probe the most important questions in astronomy, including the birth of stars and planetary systems in our Milky Way, the mysteries of black holes, and the genesis of galaxies.

Detailed information about the GMT design and science goals is online at http://www.gmto.org/

Original Source: UA News Release

Satellite View of Istanbul

Radar satellite view of Istanbul. Image credit: ESA. Click to enlarge.
The city of Istanbul, located astride the eastern edge of Europe and western edge of the Asian continent, shown in an Envisat radar multi-temporal composite image.

What is today Europe’s third largest urban centre has been a major city for the last two thousand years. It has known three different names in that time: Byzantium when it was the gateway to Greek settlements on the Black Sea, Constantinople when it became the capital of the Eastern Roman Empire, then Istanbul when it fell to Muslim invaders in 1453.

In 1919 Istanbul lost its position as capital of Turkey, but remains that country’s leading economic centre. Its population has grown from 2.84 million in 1970 to around ten million today, with settlers flocking from rural areas of Anatolia. Around 30% of all the cars owned in Turkey are in Istanbul.

Urban areas show up as white in this image ? the brightest areas being the most densely built-up. Among the densest is the old town, located on the west side of the city on the Emin?nu Peninsula, below the river estuary known as the Golden Horn. Further west along the coast are the runways of Ataturk International Airport.

Istanbul owes its prosperity to its status as a link between the Balkans, the Middle East and Central Asia, and to the high level of shipping that travels through the narrow Bosporus (Bosphorus) channel dividing Europe and Asia.

Some 48 000 ships pass through the Bosporus annually, three times denser than the Suez Canal traffic and four times as dense as the Panama Canal. Around 55 million tonnes of oil are shipped through here each year. Look closely along the Bosporus and bright points from individual ships can be seen. Also visible are the two bridges connecting the two continents, crossed by at least 45 000 vehicles daily.

Note the chain of islands known as the Princes’ Islands (Kizil Islands) off the east side of Istanbul. The city faces onto the inland Sea of Marmara (Marmara Denizi), which has an area of around 11 350 square kilometres. The Bosporus links the Sea to the Black Sea. Note also Lake Iznik (Iznik Golu) towards the south-east corner of the image.

Because radar images measure surface texture rather than reflected light, there is no colour in a standard radar image.

Instead the colour in this image is due to it being a multitemporal composite, made up of three Advanced Synthetic Aperture Radar (ASAR) images acquired on different dates, with separate colours assigned to each acquisition to highlight differences between them: Red for 31 July 2003, Green for 17 April 2003 and blue for 26 February 2004.

The view was acquired in ASAR Image Mode Precision, with pixel sampling of 12.5 metres.

Original Source: ESA News Release

Cebreros is Ready and Listening

The European Space Agency’s Cebreros radio telescope in Spain. Image credit: ESA. Click to enlarge.
On 9 June, a powerful new 35-metre antenna, presently undergoing acceptance testing at Cebreros, Spain, successfully picked up signals and tracked Rosetta and SMART-1. It is ESA’s second deep-space ground station in its class and adds Ka-band reception capability and high pointing precision to the ESTRACK network.

Construction of the new ground station, located in the Spanish province of Avila, has proceeded in record time. Procurement activities started in February 2003, and in spring 2004, on-site work was initiated.

After successful assembly of the antenna structure in November 2004 and the acceptance testing of radio-frequency components, the system is now entering final on-site testing. All portions of the antenna’s infrastructure, including power systems, buildings and communications, are already complete and are ready to hand over for operations.

Tuned in to signals from distant space
Successful reception of signals from the two spacecraft demonstrates that the antenna is working well. Rosetta, Europe’s comet-chaser, is presently 46 million km from Earth while SMART-1 is orbiting the Moon.

Cebreros will be capable of receiving signals in the X and Ka bands. The X band (7-8 GHz) is used for routine telecommanding and to transmit high-volume data to Earth; the Ka band (32 GHz) offers enhanced data reception rates and will be used for future missions.

Additional measurements using radio-emitting stars gave good first results with respect to pointing accuracy and antenna performance, indicating that the station’s specifications will be met.

Full operational readiness of the antenna is anticipated for 30 September 2005, and Cebreros is subsequently scheduled to swing into operation to support the Venus Express mission, scheduled for launch on 26 October 2005.

With Cebreros, Spain, and New Norcia, Australia, ESA spacecraft operations will benefit from two 35-metre deep-space antennas. Future plans foresee the possible construction of a third 35-metre station at an American longitude to become ready by the end of 2009.

ESTRACK family grows
Cebreros is the latest station to join ESTRACK, ESA’s worldwide network of ground stations operated from the agency’s Space Operations Centre (ESOC) in Darmstadt, Germany. Ground stations are used for sending commands to spacecraft and receiving data from onboard instruments.

With Cebreros, there are 8 stations in ESTRACK, located in Europe, Africa, South America and Australia. Additional stations in Kenya, Chile and Norway are available when needed. The system is highly automated and most stations run with little or no manned intervention for routine operations, providing a significant cost benefit.

Original Source: ESA News Release

Planets Under Construction

Artist illustratino of a planetary zone filled with pebbles. Image credit: CfA. Click to enlarge.
Interstellar travelers might want to detour around the star system TW Hydrae to avoid a messy planetary construction site. Astronomer David Wilner of the Harvard-Smithsonian Center for Astrophysics (CfA) and his colleagues have discovered that the gaseous protoplanetary disk surrounding TW Hydrae holds vast swaths of pebbles extending outward for at least 1 billion miles. These rocky chunks should continue to grow in size as they collide and stick together until they eventually form planets.

“We’re seeing planet building happening right before our eyes,” said Wilner. “The foundation has been laid and now the building materials are coming together to make a new solar system.”

Wilner used the National Science Foundation’s Very Large Array to measure radio emissions from TW Hydrae. He detected radiation from a cold, extended dust disk suffused with centimeter-sized pebbles. Such pebbles are a prerequisite for planet formation, created as dust collects together into larger and larger clumps. Over millions of years, those clumps grow into planets.

“We’re seeing an important step on the path from interstellar dust particles to planets,” said Mark Claussen (NRAO), a co-author on the paper announcing the discovery. “No one has seen this before.”

A dusty disk like that in TW Hydrae tends to emit radio waves with wavelengths similar to the size of the particles in the disk. Other effects can mask this, however. In TW Hydrae, the astronomers explained, both the relatively close distance of the system and the stage of the young star’s evolution are just right to allow the relationship of particle size and wavelength to prevail. The scientists observed the young star’s disk with the VLA at several centimeter-range wavelengths. “The strong emission at wavelengths of a few centimeters is convincing evidence that particles of about the same size are present,” Claussen said.

Not only does TW Hydrae show evidence of ongoing planet formation, it also shows signs that at least one giant planet may have formed already. Wilner’s colleague, Nuria Calvet (CfA), has created a computer simulation of the disk around TW Hydrae using previously published infrared observations. She showed that a gap extends from the star out to a distance of about 400 million miles – similar to the distance to the asteroid belt in our solar system. The gap likely formed when a giant planet sucked up all the nearby material, leaving a hole in the middle of the disk.

Located about 180 light-years away in the constellation Hydra the Water Snake, TW Hydrae consists of a 10 million-year-old star about four-fifths as massive as the Sun. The protoplanetary disk surrounding TW Hydrae contains about one-tenth as much material as the Sun – more than enough to form one or more Jupiter-sized worlds.

“TW Hydrae is unique,” said Wilner. “It’s nearby, and it’s just the right age to be forming planets. We’ll be studying it for decades to come.”

This research was published in the June 20, 2005, issue of The Astrophysical Journal Letters.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: Harvard CfA News Release

Pan’s Influence on the Rings

Saturn’s moon Pan makes ripples in the rings as it orbits the planet. Image credit: NASA/JPL/SSI. Click to enlarge.
Saturn’s moon Pan is seen here orbiting within the Encke Gap in Saturn’s A ring in two differently processed versions of the same Cassini image. The little moon is responsible for clearing and maintaining this gap, named for Johann Franz Encke, who discovered it in 1837. Pan is 20 kilometers (12 miles) across.

The top image reveals two of the faint, dusty ringlets that occupy the gap along with Pan. One of the ringlets occupies nearly the same orbit as Pan, while the other is closer to the gap’s inner edge. Not only do the ringlets vary in brightness, but they also appear to move in and out along their length, resulting in notable “kinks,” which are similar in appearance to those observed in the F ring (see PIA06585). One possible explanation for the complex structure of the ringlets is that Pan may not be the only moonlet in this gap.

Pan is responsible for creating stripes, called ‘wakes,’ in the ring material on either side of it. Since ring particles closer to Saturn than Pan move faster in their orbits, these particles pass the moon and receive a gravitational “kick” from Pan as they do. This kick causes waves to develop in the gap where the particles have recently interacted with Pan (see PIA06099), and also throughout the ring, extending hundreds of kilometers into the rings. These waves intersect downstream to create the wakes, places where ring material has bunched up in an orderly manner thanks to Pan’s gravitational kick.

In the bottom image, the bright stripes or wakes moving diagonally away from the gap’s edges can be easily seen. The particles near the inner gap edge have most recently interacted with Pan and have just passed the moon. Because of this, the disturbances caused by Pan on the inner gap edge are ahead of the moon. The reverse is true at the outer edge: the particles have just been overtaken by Pan, leaving the wakes behind it.

This image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 18, 2005, at a distance of approximately 1.6 million kilometers (1 million miles) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 44 degrees. The image scale is 9 kilometers (6 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. For additional images visit the Cassini imaging team homepage http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Bumpy Dust Makes Molecular Hydrogen

Simulation of interstellar grains of dust. Image credit: OSU. Click to enlarge.
Science fiction writer Harlan Ellison once said that the most common elements in the universe are hydrogen and stupidity.

While the verdict is still out on the volume of stupidity, scientists have long known that hydrogen is indeed by far the most abundant element in the universe. When they peer through their telescopes, they see hydrogen in the vast clouds of dust and gas between stars ?- especially in the denser regions that are collapsing to form new stars and planets.

But one mystery has remained: why is much of that hydrogen in molecular form ?- with two hydrogen atoms bonded together ?- rather than its single atomic form? Where did all that molecular hydrogen come from? Ohio State University researchers recently decided to try to figure it out.

They discovered that one seemingly tiny detail — whether the surfaces of interstellar dust grains are smooth or bumpy — could explain why there is so much molecular hydrogen in the universe. They reported their results at the 60th International Symposium on Molecular Spectroscopy, held at Ohio State University .

Hydrogen is the simplest atomic element known; it consists of just one proton and one electron. Scientists have always taken for granted the existence of molecular hydrogen when forming theories about where all the larger and more elaborate molecules in the universe came from. But nobody could explain how so many hydrogen atoms were able to form molecules — until now.
When it comes to making molecular hydrogen, the ideal microscopic host surface is ?less like the flatness of Ohio and more like a Manhattan skyline.?

For two hydrogen atoms to have enough energy to bond in the cold reaches of space, they first have to meet on a surface, explained Eric Herbst, Distinguished University Professor of physics at Ohio State.

Though scientists suspected that space dust provided the necessary surface for such chemical reactions, laboratory simulations of the process never worked. At least, they didn’t work well enough to explain the full abundance of molecular hydrogen that scientists see in space.

Herbst, professor of physics, chemistry, and astronomy, joined with Herma Cuppen, a postdoctoral researcher, and Qiang Chang, a doctoral student, both in physics, to simulate different dust surfaces on a computer. They then modeled the motion of two hydrogen atoms tumbling along the different surfaces until they found one another to form a molecule.

Given the amount of dust that scientists think is floating in space, the Ohio State researchers were able to simulate the creation of the right amount of hydrogen, but only on bumpy surfaces.

When it comes to making molecular hydrogen, the ideal microscopic host surface is ?less like the flatness of Ohio and more like a Manhattan skyline,? Herbst said.

The problem with past simulations, it seems, is that they always assumed a flat surface.

Cuppen understands why. ?When you want to test something, starting with a flat surface is just faster and easier,? she said

She should know. She’s an expert in surface science, yet it still took her months to assemble the bumpy dust model, and she’s still working to refine it. Eventually, other scientists will be able to use the model to simulate other chemical reactions in space.

In the meantime, the Ohio State scientists are collaborating with colleagues at other institutions who are producing and using actual bumpy surfaces that mimic the texture of space dust. Though real space dust particles are as small as grains of sand, these larger, dime-sized surfaces will enable scientists to test whether different textures help molecular hydrogen to form in the lab.

Original Source: OSU News Release

Sea Launch Launches Americas-8 Satellite

Zenit-3SL rocket blasting off with Intelsat Americas-8 satellite. Image credit: Boeing. Click to enlarge.
Sea Launch Company today successfully delivered the Intelsat Americas?-8 (IA-8) communications satellite to geosynchronous transfer orbit. Early data indicate the spacecraft is in excellent condition.

A Zenit-3SL vehicle lifted off at 7:03 am PDT ( 14:03 GMT), from the Odyssey Launch Platform, positioned at 154 degrees West Longitude. All systems performed nominally throughout the flight. The Block DM-SL upper stage inserted the 5,500 kg (12,125 lbs.) satellite to geosynchronous transfer orbit, on its way to a final orbital position of 89 degrees West Longitude. A ground station in Fucino, Italy, acquired the spacecraft?s first signal less than an hour after liftoff, as planned.

This mission is Sea Launch?s fifth launch for Space Systems/Loral (SS/L), the spacecraft?s manufacturer, and the first for Intelsat. The IA-8 satellite is designed to provide expanded coverage over the Americas, the Caribbean, Hawaii and Alaska with voice, video and data transmission and distribution services. SS/L?s 1300 bus carries 28 C-band and 36 Ku-band transponders, as well as 24 Ka-band spot beams and has a total end-of-life power of 16 Kw. IA-8 is the fifth Intelsat satellite in the North American arc and the 28 th satellite in Intelsat?s global fleet.

Following acquisition of the spacecraft?s signal, Jim Maser, president and general manager of Sea Launch, congratulated Space Systems/Loral and Intelsat. ?We are thrilled to welcome Intelsat into our growing family of satisfied customers,? Maser said. ?We look forward to future missions with Intelsat as well as with our long-time colleagues at Space Systems/Loral. The Sea Launch team has successfully met our commitments once again and I want to personally thank them for their unwavering commitment and hard work.?

Sea Launch Company, LLC, headquartered in Long Beach, Calif., and marketed through Boeing Launch Services (www.boeing.com/launch), is the world?s most reliable heavy-lift commercial launch service. This international partnership offers the most direct and cost-effective route to geostationary orbit. With the advantage of a launch site on the Equator, the reliable Zenit-3SL rocket can lift a heavier spacecraft mass or provide longer life on orbit, offering best value plus schedule assurance. For additional information and images of this successfully completed mission, visit the Sea Launch website at: www.sea-launch.com

Original Source: Boeing News Release

June 25th Conjunction: Mercury, Venus and Saturn

Sky map of the June 25th planetary alignment. Image credit: NASA. Click to enlarge.
Saturn, which has been prominent, in the constellation Gemini all winter is slowly exiting our skies. But the Ringed Planet has one last show to put on for us, and the stage has been set. On June 18th, Saturn was joined by Venus, followed by Mercury on the 19th. On these dates the trio formed a long string stretching from the stars Castor and Pollux to just above the horizon. As the week progressed, the two faster planets slowly drew closer to Saturn. On the evenings of the 24th and 25th the trio will form a very close conjunction with Venus being just 1 degree from Saturn and less than 1 degree from Mercury.

For the next few nights all 3 planets should be visible in the wide field of view of a pair of binoculars or small telescope. By the 27th, Mercury and Venus will have drawn away from Saturn somewhat but will lie just 8 arc-minutes from one another, nearly indistinguishable to the unaided eye.

As June turns to July, Saturn will be lost in the glare of the setting sun. But Mercury and Venus will stay in close conjunction well into the month. On July 8th look for a very slim waxing crescent moon hovering just above the pair. Around July 15th the apparent separation of Mercury and Venus will have increased to 5 degrees. At this point Mercury will begin looping back toward the sun, while Venus continues to climb higher in our evening skies.

Contrary to popular belief, planetary conjunctions are fairly common. All the planets and the sun appear to travel along an imaginary line in the sky known as the ecliptic. Because our solar system is essentially a disk, the objects in our solar system appear to follow the same path year after year after year. Since we see these objects from Earth, which is itself moving, the planets occasionally appear to get close together in the sky. Conjunctions of 2 or 3 planets happen quite often particularly when one of them is Venus. The faster planets seem to ?catch up with? and ?pass? the slower moving ones, as we see in June.

Throughout recorded history humans have observed planetary conjunctions. In ancient times they were thought to be signs or omens. Not until recent centuries have we been able to model and therefore marvel at the workings of our solar system. Even though the conjunction of Mercury, Venus and Saturn doesn?t portend events, it is nonetheless a spectacular sight to behold.

Written by Rod Kennedy

New Form of Matter Created

A rotating superfluid gas of fermions pierced with vortices. Image credit: MIT. Click to enlarge.
MIT scientists have brought a supercool end to a heated race among physicists: They have become the first to create a new type of matter, a gas of atoms that shows high-temperature superfluidity.

Their work, to be reported in the June 23 issue of Nature, is closely related to the superconductivity of electrons in metals. Observations of superfluids may help solve lingering questions about high-temperature superconductivity, which has widespread applications for magnets, sensors and energy-efficient transport of electricity, said Wolfgang Ketterle, a Nobel laureate who heads the MIT group and who is the John D. MacArthur Professor of Physics.

Seeing the superfluid gas so clearly is such a dramatic step that Dan Kleppner, director of the MIT-Harvard Center for Ultracold Atoms, said, “This is not a smoking gun for superfluidity. This is a cannon.”

For several years, research groups around the world have been studying cold gases of so-called fermionic atoms with the ultimate goal of finding new forms of superfluidity. A superfluid gas can flow without resistance. It can be clearly distinguished from a normal gas when it is rotated. A normal gas rotates like an ordinary object, but a superfluid can only rotate when it forms vortices similar to mini-tornadoes. This gives a rotating superfluid the appearance of Swiss cheese, where the holes are the cores of the mini-tornadoes. “When we saw the first picture of the vortices appear on the computer screen, it was simply breathtaking,” said graduate student Martin Zwierlein in recalling the evening of April 13, when the team first saw the superfluid gas. For almost a year, the team had been working on making magnetic fields and laser beams very round so the gas could be set in rotation. “It was like sanding the bumps off of a wheel to make it perfectly round,” Zwierlein explained.

“In superfluids, as well as in superconductors, particles move in lockstep. They form one big quantum-mechanical wave,” explained Ketterle. Such a movement allows superconductors to carry electrical currents without resistance.

The MIT team was able to view these superfluid vortices at extremely cold temperatures, when the fermionic gas was cooled to about 50 billionths of a degree Kelvin, very close to absolute zero (-273 degrees C or -459 degrees F). “It may sound strange to call superfluidity at 50 nanokelvin high-temperature superfluidity, but what matters is the temperature normalized by the density of the particles,” Ketterle said. “We have now achieved by far the highest temperature ever.” Scaled up to the density of electrons in a metal, the superfluid transition temperature in atomic gases would be higher than room temperature.

Ketterle’s team members were MIT graduate students Zwierlein, Andre Schirotzek, and Christian Schunck, all of whom are members of the Center for Ultracold Atoms, as well as former graduate student Jamil Abo-Shaeer.

The team observed fermionic superfluidity in the lithium-6 isotope comprising three protons, three neutrons and three electrons. Since the total number of constituents is odd, lithium-6 is a fermion. Using laser and evaporative cooling techniques, they cooled the gas close to absolute zero. They then trapped the gas in the focus of an infrared laser beam; the electric and magnetic fields of the infrared light held the atoms in place. The last step was to spin a green laser beam around the gas to set it into rotation. A shadow picture of the cloud showed its superfluid behavior: The cloud was pierced by a regular array of vortices, each about the same size.

The work is based on the MIT group’s earlier creation of Bose-Einstein condensates, a form of matter in which particles condense and act as one big wave. Albert Einstein predicted this phenomenon in 1925. Scientists later realized that Bose-Einstein condensation and superfluidity are intimately related.

Bose-Einstein condensation of pairs of fermions that were bound together loosely as molecules was observed in November 2003 by independent teams at the University of Colorado at Boulder, the University of Innsbruck in Austria and at MIT. However, observing Bose-Einstein condensation is not the same as observing superfluidity. Further studies were done by these groups and at the Ecole Normale Superieure in Paris, Duke University and Rice University, but evidence for superfluidity was ambiguous or indirect.

The superfluid Fermi gas created at MIT can also serve as an easily controllable model system to study properties of much denser forms of fermionic matter such as solid superconductors, neutron stars or the quark-gluon plasma that existed in the early universe.

The MIT research was supported by the National Science Foundation, the Office of Naval Research, NASA and the Army Research Office.

Original Source: MIT News Release

Extrasolar Planet Reshapes Ring Around a Star

Hubble image of the ring around Fomalhaut. Image credit: Hubble. Click to enlarge.
NASA Hubble Space Telescope’s most detailed visible-light image ever taken of a narrow, dusty ring around the nearby star Fomalhaut (HD 216956), offers the strongest evidence yet that an unruly and unseen planet may be gravitationally tugging on the ring.

Hubble unequivocally shows that the center of the ring is a whopping 1.4 billion miles (15 astronomical units) away from the star. This is a distance equal to nearly halfway across our solar system. The most plausible explanation, astronomers said, is that an unseen planet moving in an elliptical orbit is reshaping the ring with its gravitational pull. The geometrically striking ring, tilted obliquely toward Earth, would not have such a great offset if it were simply being influenced by Fomalhaut’s gravity alone.

An offset of the ring center from the star has been inferred from previous and longer wavelength observations using submillimeter telescopes on Mauna Kea, Hawaii, the Spitzer Space Telescope, Caltech’s Submillimeter Observatory and applying theoretical modeling and physical assumptions. Now Hubble’s sharp images directly reveal the ring’s offset from Fomalhaut.

These new observations provide strong evidence that at least one unseen planetary mass object is orbiting the star. Hubble would have detected an object larger than a planet, such as a brown dwarf. “Our new Hubble images confirm those earlier hypotheses that proposed a planet was perturbing the ring,” said Paul Kalas of the University of California at Berkeley. The ring is similar to our solar system’s Kuiper Belt, a vast reservoir of icy material left over from the formation of our solar system planets.

The observations offer insights into our solar system’s formative years, when the planets played a game of demolition derby with the debris left over from the formation of our planets, gravitationally scattering many objects across space. Some icy material may have collided with the inner solar system planets, irrigating them with water formed in the colder outer solar system. Other debris may have traveled outward, forming the Kuiper Belt and the Oort Cloud, a spherical cloud of material surrounding the solar system.

Only Hubble has the exquisite optical resolution to resolve that the ring’s inner edge is sharper than its outer edge, a telltale sign that an object is gravitationally sweeping out material like a plow clearing away snow. Another classic signature of a planet’s influence is the ring’s relatively narrow width, about 2.3 billion miles (25 astronomical units). Without an object to gravitationally keep the ring material intact, astronomers said, the particles would spread out much wider.

“What we see in this ring is similar to what is seen in the Cassini spacecraft images of Saturn’s narrow rings. In those images, Saturn’s moons are ‘shepherding’ the ring material and keeping the ring from spreading out,” Kalas said.

The suspected planet may be orbiting far away from Fomalhaut, inside the dust ring’s inner edge, between 4.7 billion and 6.5 billion miles (50 to 70 astronomical units) from the star. The ring is 12 billion miles (133 astronomical units) from Fomalhaut, which is much farther away than our outermost planet Pluto is from the Sun. These Hubble observations do not detect the putative planet directly, so the astronomers cannot measure its mass. They will, instead, conduct computer simulations of the ring’s dynamics to estimate the planet’s mass.

Kalas and collaborators James R. Graham of the University of California at Berkeley and Mark Clampin of the NASA Goddard Space Flight Center in Greenbelt, Md., will publish their findings in the June 23, 2005 issue of the journal Nature.

Fomalhaut, a 200-million-year-old star, is a mere infant compared to our own 4.5-billion-year-old Sun. It resides 25 light-years away from the Sun. Located in the constellation Piscis Austrinus (the Southern Fish), the Fomalhaut ring is ten times as old as debris disks seen previously around the stars AU Microscopii and Beta Pictoris, where planets may still be forming. If our solar system is any example, planets should have formed around Fomalhaut within tens of millions of years after the birth of the star.

The Hubble images also provide a glimpse of the outer planetary region surrounding a star other than our Sun. Many of the more than 100 planets detected beyond our solar system are orbiting close to their stars. Most of the current planet-detecting techniques favor finding planets that are close to their stars.

“The size of Fomalhaut’s dust ring suggests that not all planetary systems form and evolve in the same way ? planetary architectures can be quite different from star to star,” Kalas explained. “While Fomalhaut’s ring is analogous to the Kuiper Belt, its diameter is four times greater than that of the Kuiper Belt.”

The astronomers used the Advanced Camera for Surveys’ (ACS) coronagraph aboard Hubble to block out the light from the bright star so they could see details in the faint ring.

“The ACS’s coronagraph offers high contrast, allowing us to see the ring’s structure against the extremely bright glare from Fomalhaut,” Clampin said. “This observation is currently impossible to do at visible wavelengths without the Hubble Space Telescope. The fact that we were able to detect it with Hubble was unexpected, but impressive.”

Kalas and his collaborators used Hubble over a five-month period in 2004 ? May 17, Aug. 2, and Oct. 27 ? to map the ring’s structure. One side of the ring has yet to be imaged because it extended beyond the ACS camera’s field of view. The astronomers will use Hubble again this summer to map the entire ring. They expect that the additional Hubble data will reveal whether or not the ring has any gaps, which could have been carved out by the gravitational influence of an unseen body. The longer, deeper exposures also may show whether the ring has an even wider diameter than currently seen. In addition, the astronomers will measure the ring’s colors to determine its physical properties, including its composition.

Previous thermal emission maps of Fomalhaut showed that one side of the ring is warmer than the other side, implying that the ring is off center by about half the distance measured by Hubble. This difference might be explained by the fact that Hubble’s ACS images of the ring’s structure are 100 times sharper than the longer wavelength observations, and hence, yield a much more accurate result. Or the discrepancy might imply that the ring’s size looks different at other wavelengths.

Fomalhaut’s dust ring was discovered in 1983 in observations made by NASA’s Infrared Astronomical Satellite (IRAS). The system is a compelling target for future telescopes such as the James Webb Space Telescope and the Terrestrial Planet Finder, Kalas said.

Original Source: Hubble News Release